277 113 Sampling Figure 11.16: Complex irnpulsc response of the interpolation filter Figure 11.17: Baird-pass spectrniii of a rcal signal The even iiuiriber condition comes about l m a u s r of the conjuga wo = 71 Aw,n cr IN (11.42) Otlicrwisc thc space in Figure 11.17 carrriot br c*ornpletely fill mcl critical sarrtplirig i s irnpossiblc Figuie 11.18 sho\’i’h the sp callg 5arnplcd signaf ant1 the t oirwpontling dclta impulse train for n = The ideal iril crpolation filter must take exactly tlir frequency tt~iiiponent~ that were contained in the original karrd-pass signal We can dehcxibe it with LI rcctaiigular frcyienc> rec;ponse in the l~as~barttl, that is shifted by coil\iohitio~twith two svmmetrical delta iinpuihes to the band-pass loca,tions: Thc correspoiiding irripiilse rcq)oiisct is piircly rcal iuid rescrnibles the impulse responw of thr interpolation filter (1I 35) but bwarise of the bend-pass cliaractcr,